Method for separation of fines from hot broken sinter

ABSTRACT

The invention is directed to the removal of granular fines or dust from broken sinter cake, before delivery thereof to a blast furnace, by subjecting the broken cake, during passage from the sinter breakers to the cooling area, to a pressurized upward blast of air which carries the sinter fines through an exhaust hood and suitable conveyor conduit into a precipitator which removes the fines for return to the sinter machine and discharges the air to the atmosphere.

United States Patent Inventors Horst Seidel Biscofsheim; Fred Cappel,Neu-lsenburg 11, both of Germany Appl. No. 810,628 Filed Mar. 26, 1969Patented Dec. 28, 1971 Assignee Dravo Corporation Pittsburgh, Pa.Priority Mar. 30, 1968 Germany P 17 58 081.3

METHOD FOR SEPARATION OF FINES FROM HOT BROKEN SINTER 3 Claims, 2Drawing Figs.

U.S. Cl 209/11, 34/57, 34/187, 75/5, 209/139, 209/466, 266/21 Int. ClB07b 4/08 Field of Search 209/1 1, 19,

References Cited UNITED STATES PATENTS 2,874,484 2/1959 Dapses 34/1873,161,485 12/1964 Buhrer 34/85 X 3,309,787 3/1967 Forsyth et al. 34/187X 3,313,534 4/1967 Frans 266/21 X 3,374,998 3/1968 266/21 3,381,9485/1968 Stirling 266/21 Primary Examiner-Frank W. Lutter AssistantExaminer-William Cuchlinski, Jr. Attorney-Parmelee, Utzler and WelshABSTRACT: The invention is directed to the removal of granular fines ordust from broken sinter cake, before delivery thereof to a blastfurnace, by subjecting the broken cake, during passage from the sinterbreakers to the cooling area, to a pressurized upward blast of air whichcarries the sinter fines through an exhaust hood and suitable conveyorconduit into a precipitator which removes the fines for return to thesinter machine and discharges the air to the atmosphere.

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SHEET 2 OF 2 INVEN TORS. HORST .SE/DEL and FRED CAPPEL At rorneys METHODFOR SEPARATION OF FINES FROM HOT BROKEN SINTER BACKGROUND OF THEINVENTION The invention is concerned with the sintering of metallic orefines for processing in a conventional blast furnace in the manufactureof steel.

BRIEF SUMMARY OF THE INVENTION The invention is concerned with theprocessing of iron ore fines for reduction in a blast furnace byagglomerating the ore fines by the known process of sintering the orefines and fuel to form sinter cakes. The sinter cakes are dischargedfrom the sintering line and broken into smaller sizes by known methods.During the breaking of the sinter cakes many fines are produced and aremixed with the larger size pieces of sinter. The charge such a mixtureinto a blast furnace would result in air pollution due to the blast airblowing said fines into the atmosphere, with consequent loss of valuableore.

One object of the invention is to provide a suitable pressurized blastof cooling air through the broken sinter cake as it moves off the sinterfeed line and through a conventional rotating sinter cooler, bycollecting such blast air above said cooler and passing it through asuitable precipitator which returns the sinter fines to the sinteringmachine for reuse and discharges the excess air to the atmosphere.

Another object of the invention is to provide means for enclosing aportion of a rotating sinter cooling means with a suitable exhaust hoodconnected with a suitable precipitator and passing a blast of air underpressure through the cooling broken sinter moving beneath said hood toremove the fines therefrom and discharge such fines into a suitableprecipitator. The collected fines are discharged from the bottom of theprecipitator and the excess dust free air within the precipitator iswithdrawn from adjacent the top of the precipitator by a suitableexhaust fan for discharge to the atmosphere.

A further object of the invention is to form the sinter cooling means asa rotating annular member which receives the crushed sinter cake fromthe sinter feed line and passing same through vertical pressurized airblast to remove the fines therefrom and discharge them into theprecipitator.

DESCRIPTION OF THE DRAWINGS FIG. I shows a side elevation of theapparatus of the invention, and

FIG. 2 shows a plan view of the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION As is wellknown in the art of making sinter, the sintered ore or other product isdischarged from the pallet in which it is formed as a coherent massreferred to as sinter cakes." These sinter cakes are discharged upon agratelike support known as grizzly bars where the cake" is engaged by asuitable tool and broken into smaller pieces, and are passed onto asinter feeder 2. During this breaking operation, considerable amounts ofstill smaller pieces known as fines are formed, which are also passedonto the sinter feeder.

In the present invention we pass the broken sinter cake and fines fromsinter feeder 2 on to a generally circular U-shaped rotating cooler 1having a perforated bottom wall. Beneath cooler perforated bottom wall,in close spaced relation thereto, for a length of about one-fifth of theperiphery thereof, there is mounted a suitable wind box or pressurechamber 3 having connected thereto an air pressure pump 4. The airstream from pump 4 and pressure chamber 3 flows vertically upwardthrough the perforated bottom wall of the rotating cooler l and thebroken sinter thereon. The fine granular portions of the sinter cakelayer are carried upwardly by the air stream into an overlying exhausthood 5 and through conduit 6 connected therewith, into a suitableprecipitator 8.

An exhaust fan 7 withdraws air from the top portion of the precipitator8 through a conduit 9 and the precipitated sinter fines are withdrawnfrom precipitator 8 through the bottom thereof for return to thesintering mechanism (not shown), for reuse in forming sinter cakes.

The pressure at which air from pump 4 is supplied to wind box 3 may bevaried in accordance with the depth of the layer of sinter upon thesinter cooler 1. Such air pressure may vary between 4 to 32 inches watercolumn pressure, preferably l6 to 24 inches water column pressure willsufiice to remove substantially all of the granular fines of 0 to 14mesh from the sinter.

The following table illustrates the comparative pressures of the airstream at the pressure pump and at the sinter layer for varying depth ofsinter upon the rotating cooler.

The arrangement as described provides many advantages over priorpractices. Thus, hot screening of the sinter for removal of fines iseliminated and a smaller granular size of return material is obtained.This results in a reduction of the recycled return material withsubstantial increase in capacity of the sintering strands, and reductionof coke used on the sintering strands. Additionally, there is anincrease in the production output of the blast furnace receiving suchsinter, due to reduction of sinter fines lost through the furnace airblast in melting. The amount of atmospheric dust is also reduced due touse of the precipitator 8 adjacent the sinter cooler. A furtheradvantage is that such a system can be installed in many existingsintering systems, with a minimum of alterations.

We claim:

1. A method for dry classification of crushed hot sinter as receivedfrom a conventional sintering machine, comprising the steps of:

feeding the crushed sinter cake in the absence of prior screening onto aconventional rotating cooling device having a perforated sinter carryingsurface,

blowing a blast of pressurized air upwardly through the bottom of theperforated surface of said cooling device for displacement of sinterfines thereon while retaining the remaining of said crushed sinter onsaid surface,

' collecting the air blast and suspended fines therein from above thetop surface of said perforated surface of said cooling device anddischarging same into a suitable precipitator to separate the fines fromsaid air blast,

continuously withdrawing the air from the upper portion of theprecipitator, and

collecting the separated fines from the bottom of said precipitator andreturning them to the moving sintering machine for incorporation intothe sintering cake forming thereon.

2. The method as defined in claim I, wherein said air blast is under apressure of 4 to 32 inches W.C. of pressure, preferably 20 to 24 inchesW.C.

3. The process as defined in claim 1 wherein said sinter fines displacedfrom the sinter layer of said air blast are less than one-eighth inch,preferably less than one thirty-second inch in size.

1. A method for dry classification of crushed hot sinter as receivedfrom a conventional sintering machine, comprising the steps of: feedingthe crushed sinter cake in the absence of prior screening onto aconventional rotating cooling device having a perforated sinter carryingsurface, blowing a blast of pressurized air upwardly through the bottomof the perforated surface of said cooling device for displacement ofsinter fines thereon while retaining the remaining of said crushedsinter on said surface, collecting the air blast and suspended finestherein from above the top surface of said perforated surface of saidcooling device and discharging same into a suitable precipitator toseparate the fines from said air blast, continuously withdrawing the airfrom the upper portion of the precipitator, and collectiNg the separatedfines from the bottom of said precipitator and returning them to themoving sintering machine for incorporation into the sintering cakeforming thereon.
 2. The method as defined in claim 1, wherein said airblast is under a pressure of 4 to 32 inches W.C. of pressure, preferably20 to 24 inches W.C.
 3. The process as defined in claim 1 wherein saidsinter fines displaced from the sinter layer by said air blast are lessthan one-eighth inch, preferably less than one thirty-second inch insize.